Cochlear Implant : Anaesthesia Challenges

Cochlear implants are now an acceptable therapeutic option for those patients with irreversible hearing loss and deaf-mutism. The surgery is time consuming and complicated. Hence, the technique of anaesthesia plays a crucial role in success of cochlear implant surgery. Cochlear implant patients have various types of syndromes which are important from anaesthetic as well as surgical point of view. Pre-implant preparation requires objective assessment of hearing, plain X-rays of skull and a CT scan of the temporal bone. Anaesthesia is required for objective assessment of hearing in children under five years of age, to obtain X-rays of skull, magnetic resonance imaging (MRI), CT scan, brain evoked response audiometry (BERA) testing and finally for cochlear implant surgery. Anaesthetic considerations include preoperative familiarisation with the patient and his family. Syndromal illnesses have specific anaesthetic significance such as presence of difficult airway or prolonged QT interval. Parental presence is highly desirable during induction of anaesthesia. Electro-surgical instruments especially monopolar ones, should not be used once the cochlear implant is in place.

In our institution, all cases (15 children) received their cochlear implants under general anaesthesia and formed the study group. Children were administered midazolam orally and inj ketamine during CT scan. Our techniques of general anaesthesia were modified to permit use of nerve stimulators during surgery. To minimise the incidence of vertigo particularly after cochleostomy, postoperative nausea and vomiting, all patients received glycopyrrolate and fentanyl citrate intravenously prior to induction. Other agents used were, thiopentone, suxamethonium and end-tidal 1.3 MAC halothane in 1:2 mixture of oxygen and nitrous oxide (O2 and N2O). Electro diathermy was switched off, before the cochlear device was implanted on the patient. Patients were allowed to breathe spontaneously whenever nerve stimulator was used to locate the facial nerve. Inj Ondansetron 0.1 mg/kg was used as anti-emetic agent. Postoperative pain relief was initially provided with fentanyl 1 μg/kg IV and later with syrup ibuprofen.

There were no remarkable anaesthetic or surgical complication in our series except perilymph leakage in two cases.